Yammers hate Brummies, and also Birmingham, and do not wish any association with them or it.
Brummies consider Yammers their estranged yokel cousins who are best left to their own devices, although the Brummies have conceded that Yammers will see sense and want to visit the city on occasion and provided them with a Metro service for that purpose.
Suttonites are snobs. :P
(And also, Kings Heath is the centre of the universe and precisely where all the cool people live, along with selected, unpretentious bits of Moseley...)
I am proud to be a Yammer. I am a Yammer born and bred. I am also proud to now be officially a Brummie by way of something so simple as a postcode, because, for all its faults and its stupid council, Birmingham is a great city. Sometimes. When it's not trying to be London.
To end, here's a little game for you. According to the wiki link by joetimewaster, this was put on a road sign shortly before work commenced on the Dudley Bypass. I'll make a CD for the first person who gets it right (herringprincess is extempt because she knows Yammers :P) or something else if you think my music taste is shit... bonus points also to anyone who admits to having read it out loud...
If yowm saft enuff ter cum down 'ere agooin wum, yowr tay ull be spile't!!.
(It should be noted there's one word in there even I'm not sure about, but I'm probably going to try and say it out loud later...)